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Vertical 6EM7 Portable Amp
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=5134
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Author:  john55 [ 16 Feb 2018, 07:21 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Suncalc wrote:
john55 wrote:
I have a couple of 1R 50W wirewound resistors
Be careful about power resistor dissipation ratings. See my write-up here: http://www.diyaudioprojects.com/Testeq/Dummy-Speaker-Load/

Gio wrote:
Hi John. Trying to drop that much constant heat across resistors inside an enclosure can be difficult. The heat buildup inside the chassis can become problematic with extended use. My suggestion is to use an oversized resistor as you noted, but to use one that will mount to the chassis or an external heatsink so you don't get heat buildup inside of the enclosure.


Just an update....Wired the two secondaries in series (9.5-10 ish volts), plus 1.2 ohm 50W resistor in series, bolted to chassis with thermal paste and all three valves heaters connected. Reading 6.2 volts. So far so good. I've run this for 2 hours in the enclosed chassis with a vented back plate. I can add more ventilation, but don't think I need to? The resistor got no hotter than 52ÂșC.

Author:  mwhouston [ 16 Feb 2018, 18:02 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

John55, all very neat.

Author:  Suncalc [ 16 Feb 2018, 18:54 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

John;

I am always in awe of your workmanship. Very well done!

Author:  john55 [ 17 Feb 2018, 02:39 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Thanks for the pat on the back. I can't wire any other way. My first job on leaving school 48 years ago was wiring Hiwatt 50's and 100's. There's a one in five chance that I wired this one. Dave Reeves (owner of Hiwatt) was a stickler for neatness.

Author:  mwhouston [ 17 Feb 2018, 07:09 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Come on Matt my bird's nest has to beat this. Think of all the wire I have saved. Lol.

And I thought I was OCD.

Author:  john55 [ 19 Feb 2018, 07:24 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

mwhouston wrote:
Come on Matt my bird's nest has to beat this. Think of all the wire I have saved. Lol.

And I thought I was OCD.


I admit it, I am a bit OCD but in this instant I think it helps as I'm fitting a 6EM7 into a wine box. (You fault mwhouston).
I would like to fit the main choke in the power supply as shown in the photo as it makes firing up and checking the amp that much easier, but I'm not sure if being that close to the amp will cause problems. I have plenty of room in the box itself. Advice please!!!

Author:  mwhouston [ 19 Feb 2018, 18:40 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Nice parts and nice layout, I think you'll be fine.

I like to think I could start a wine box build following. Here they are $9 and I can get them just down the road. No problems drilling large holes for valve sockets. As you saw I stained one but left the other natural. Having the external tranni box and its a universal tranni box seperate, means less chance of hum and you save about $100 a build being able to use the same tranni box.

My next is SE UL KT88 with JJ Blue glass KT88s. Plus matching speakers 4" 92db effcient dual cone drivers in vertical wine boxes all matching.

Can't wait to see your amp finished. Is the wine box blonde wood or dark or are you staining?

Author:  mwhouston [ 19 Feb 2018, 18:50 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Slightly off thread I spent some weeks in Spain just a few years back. It was part of a 5.5 week adventure. Stayed in Madrid, Toledo and then Barcelona. Absolutely loved it, go back tomorrow.

Got introduce to baby eels on bread with salsa and tomatoes. And of course lots of sangria. Being a Mason and the Templar knights being active in the region centries ago held special interest.

Author:  john55 [ 20 Feb 2018, 13:33 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Looking forward to seeing your wine box amp and speakers matching set.
A six week wait for the output transformers from Edcor so I've robbed a pair from a Lacewood V2.
Hopefully I'll have the 6EM7 finished by the weekend and will put up photos. Again it's a little OCD, but it will probably go in a friends restaurant later on.
Sounds like you enjoyed Spain. It's a lovely country to work and live in.

Author:  mwhouston [ 20 Feb 2018, 16:48 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

If the amp goes in a restaurant you will need very effcient speakers to get any volume. What have you in mind? I would suggest the 12" concentric Spainish Beymas. 98db efficient and in a good side box lots of bass and volume.

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